The present invention relates to capsule package for containing a substance for preparation of a beverage in an extraction machine with a fluid under pressure.
There are several reasons for the use of capsules for the preparation of a beverage from a powder-form substance, above all in the field of espresso-type coffees extracted under pressure, namely, hygiene, optimal keeping of the coffee, ease of use, better control of the quality of the coffee obtained and good reproducibility of the extraction conditions.
These capsules can be made in an "open," form with permeable upper and lower faces to allow the extraction fluid to pass through.
In order to maintain the quality of the coffee by protecting it against moisture and oxygen, "open," capsules have to be wrapped in fluid-type bags or provided with fluid-tight peelable covers on both faces.
In order to satisfy the requirements of various countries concerning the recycling of packaging materials, there is a need for a new capsule design using lightweight materials, for example plastic films.
In order, on the other hand, to satisfy economic and commercial requirements also, the capsules should be able to be made on the same packaging machines and extracted in the same extraction machine.
Finally, to reduce the consumption of material in the manufacture of the capsules, the capsules themselves should be simplified. This can be done, for example, by eliminating the filter at the base of the capsule.
The use on ecological or economic grounds of thin flexible materials for the production of capsules, for example containing ground coffee and designed for extraction under the pressure of hot water, generally involves the problem of giving the capsules a predetermined shape to allow correct extraction of the powder-form substance and, above all, maintaining that shape after handling, transport and storage.
Now, in the interests of good extraction, the capsules must be able perfectly to follow the inner shape of the extraction system to avoid any preferential passage of water outside the layer, for example of coffee.
Filter paper capsules containing compacted ground coffee are described, for example, in Swiss Patent No. 527 592 and in European Patent Application Publication No. 0 272 432.
Compacted capsules of this type have disadvantages, namely:
because the coffee has to be compacted, there is a risk that it may not be properly wetted during extraction, resulting in incomplete extraction; PA1 since the filter paper is not deformable, it can tear and thus jeopardize the fluid tightness of the extraction process; and PA1 the capsules require specific adaptors which exactly follow their shape to obtain the fluid-tightness required for extraction.